She said she...

Laura
At my 20 week scan, we told the doctor that we didn't want to know the sex. 
When she carried out the scan we both noticed that she said 'she'. 
Is this common? Do doctors just call babies he or she? Or do you think she might have slipped? 
Baby was in an awkward position so couldn't see very much to be honest, but now I'm wondering if I should find out because now I've heard 'she' I want it confirmed! 
Thanks guys